Field of the Invention
The present invention relates to an imaging device that outputs focal point detection information and image information, and a method of driving the imaging device.
Description of the Related Art
As an imaging device in a phase difference detection system, which outputs a signal that can be used for focal point detection, an imaging device having pixels arranged in a two-dimensional matrix manner, the pixels having a pair of photoelectric conversion units arranged under a micro lens, is proposed.
Japanese Patent Application Laid-Open No. 2013-211833 describes an imaging device in which a focal point detection region from which both of the focal point detection information and the image information are acquired, and an image region from which only the image information is acquired, are provided to an imaging region. The imaging device reads out, from pixels in the focal point detection region, a signal (A signal) based on only one of the pair of photoelectric conversion units, and a signal ((A+B) signal) based on electric charges caused in both of the pair of photoelectric conversion units. Following that, the imaging device calculates these signals to acquire a signal (B signal) based on only the other photoelectric conversion unit of the pair of photoelectric conversion units, and performs the focal point detection using the A signal and the B signal. The (A+B) signal is used as an image signal as it is. Further, only the (A+B) signal is read out without reading out the A signal from pixels of the image region, whereby a decrease in a read time is realized.
However, a larger number of noise components are superimposed on the (A+B) signal read out from the focal point detection region than the (A+B) signal read out from the image region, and thus image quality may be deteriorated. Further, it is necessary to change a method of scanning rows between in the focal point detection region and in the image region in one frame period, and thus a control method is difficult.